text: #ifndef __LINUX_COMPILER_H
  #error "Please don't include <linux/compiler-gcc.h> directly, include <linux/compiler.h> instead."
  #endif
  
  /*
   * Common definitions for all gcc versions go here.
   */
  #define GCC_VERSION (__GNUC__ * 10000 \
  		   + __GNUC_MINOR__ * 100 \
  		   + __GNUC_PATCHLEVEL__)
  
  
  /* Optimization barrier */
  /* The "volatile" is due to gcc bugs */
  #define barrier() __asm__ __volatile__("": : :"memory")
  
  /*
   * This macro obfuscates arithmetic on a variable address so that gcc
   * shouldn't recognize the original var, and make assumptions about it.
   *
   * This is needed because the C standard makes it undefined to do
   * pointer arithmetic on "objects" outside their boundaries and the
   * gcc optimizers assume this is the case. In particular they
   * assume such arithmetic does not wrap.
   *
   * A miscompilation has been observed because of this on PPC.
   * To work around it we hide the relationship of the pointer and the object
   * using this macro.
   *
   * Versions of the ppc64 compiler before 4.1 had a bug where use of
   * RELOC_HIDE could trash r30. The bug can be worked around by changing
   * the inline assembly constraint from =g to =r, in this particular
   * case either is valid.
   */
  #define RELOC_HIDE(ptr, off)					\
    ({ unsigned long __ptr;					\
      __asm__ ("" : "=r"(__ptr) : "0"(ptr));		\
      (typeof(ptr)) (__ptr + (off)); })
  
  /* Make the optimizer believe the variable can be manipulated arbitrarily. */
  #define OPTIMIZER_HIDE_VAR(var) __asm__ ("" : "=r" (var) : "0" (var))
  
  #ifdef __CHECKER__
  #define __must_be_array(arr) 0
  #else
  /* &a[0] degrades to a pointer: a different type from an array */
  #define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
  #endif
  
  /*
   * Force always-inline if the user requests it so via the .config,
   * or if gcc is too old:
   */
  #if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \
      !defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4)
  # define inline		inline		__attribute__((always_inline)) notrace
  # define __inline__	__inline__	__attribute__((always_inline)) notrace
  # define __inline	__inline	__attribute__((always_inline)) notrace
  #else
  /* A lot of inline functions can cause havoc with function tracing */
  # define inline		inline		notrace
  # define __inline__	__inline__	notrace
  # define __inline	__inline	notrace
  #endif
  
  #define __deprecated			__attribute__((deprecated))
  #define __packed			__attribute__((packed))
  #define __weak				__attribute__((weak))
  #define __alias(symbol)		__attribute__((alias(#symbol)))
  
  /*
   * it doesn't make sense on ARM (currently the only user of __naked) to trace
   * naked functions because then mcount is called without stack and frame pointer
   * being set up and there is no chance to restore the lr register to the value
   * before mcount was called.
   *
   * The asm() bodies of naked functions often depend on standard calling conventions,
   * therefore they must be noinline and noclone.  GCC 4.[56] currently fail to enforce
   * this, so we must do so ourselves.  See GCC PR44290.
   */
  #define __naked				__attribute__((naked)) noinline __noclone notrace
  
  #define __noreturn			__attribute__((noreturn))
  
  /*
   * From the GCC manual:
   *
   * Many functions have no effects except the return value and their
   * return value depends only on the parameters and/or global
   * variables.  Such a function can be subject to common subexpression
   * elimination and loop optimization just as an arithmetic operator
   * would be.
   * [...]
   */
  #define __pure				__attribute__((pure))
  #define __aligned(x)			__attribute__((aligned(x)))
  #define __printf(a, b)			__attribute__((format(printf, a, b)))
  #define __scanf(a, b)			__attribute__((format(scanf, a, b)))
  #define  noinline			__attribute__((noinline))
  #define __attribute_const__		__attribute__((__const__))
  #define __maybe_unused			__attribute__((unused))
  #define __always_unused			__attribute__((unused))
  
  #define __gcc_header(x) #x
  #define _gcc_header(x) __gcc_header(linux/compiler-gcc##x.h)
  #define gcc_header(x) _gcc_header(x)
  #include gcc_header(__GNUC__)
  
  #if !defined(__noclone)
  #define __noclone	/* not needed */
  #endif
  
  /*
   * A trick to suppress uninitialized variable warning without generating any
   * code
   */
  #define uninitialized_var(x) x = x
  
  #define __always_inline		inline __attribute__((always_inline))
  